1. Field of the Invention
The present invention relates to an air-cooled type intercooler for a supercharged internal combustion engine for a vehicle.
2. Description of the Related Art
In a supercharged internal combustion engine, an intercooler is advantageously arranged downstream of the supercharger, such as a turbocharger, to decrease the temperature of air introduced into the engine from the turbocharger. The decreased air temperature decreases the occurrence of knocking, even when a high compression ratio is employed. Furthermore, the air density is increased and thus the volumetric efficiency is increased. Due to the high compression ratio and high volumetric efficiency, an increased engine power is obtained, which is the intrinsic object of employing a supercharged system.
In the prior art, an air cooled type intercooler was proposed, wherein a pair of air tanks are connected to the supercharger and the engine, respectively, and a core having a plurality of juxtaposed heat-exchanging pipes connect the tanks to each other. In the prior art construction, the heat exchanger pipes are juxtaposed in the vertical direction and each heat exchanger pipe extends in a horizontal direction. The elongation of the core in the horizontal direction to accommodate the extension of the heat exchanger pipes is larger than the elongation of the core in the vertical direction to accommodate the juxtaposed pipes. That the horizontal elongation should be larger than the vertical elongation is inevitable, since the space for arranging the intercooler, which is located in the front portion of the engine room at a position between the radiator and radiator grille or air dam skirt, also is elongated in the horizontal direction rather than in the vertical direction. However, this construction causes the length of the heat exchanger pipes, which have a limited diameter, to be increased, and thus a large pressure drop is generated when air is passed through the heat exchanger pipes. The large pressure drop requires an increase of the pressure at the output of the turbocharger, to obtain the necessary engine output power. This means that the turbocharger must be rotated at a high rotational speed, which has an adverse effect on the reliability of the turbocharger over a long period of operation.